The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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What Happens to Side Effects When You Stop Mounjaro?
When you stop taking Mounjaro (tirzepatide), the medication gradually leaves your system over several weeks. Many people wonder whether the side effects they experienced—such as nausea or constipation—will continue, or whether new symptoms might emerge. The short answer is that most Mounjaro side effects resolve fairly quickly once you stop taking it, though some effects like weight regain can take longer to become apparent. This guide explains what to expect after stopping, and how Mounjaro's withdrawal profile compares to Wegovy, the alternative GLP-1 prescription injection available in the UK.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Side Effect Resolution and Weight Changes After Stopping
Gastrointestinal side effects such as nausea, diarrhoea, constipation, and stomach pain typically resolve within 1–2 weeks of your final Mounjaro KwikPen injection. Since tirzepatide is a once-weekly medication, most people experience rapid improvement in digestive symptoms once the active dose is no longer being administered. Appetite suppression and the sense of fullness usually diminish over the same timeframe.
However, weight regain often begins within weeks of stopping treatment. Clinical trial data from SURMOUNT studies showed that without continued lifestyle changes (reduced-calorie diet and increased physical activity), participants who stopped tirzepatide gradually returned to their baseline weight. The rate of weight regain varies significantly between individuals and depends on whether dietary and exercise habits remain consistent. Some people maintain their progress; others experience steady weight increase over 3–6 months if calorie intake returns to pre-treatment levels.
Mood changes or fatigue that developed during treatment also tend to reverse quickly. Hair loss (alopecia), reported by some users, typically stabilises within weeks of stopping, though new hair growth may take months to become visible.
Clinically BackedWeight Loss
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
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Mounjaro vs Wegovy: Stopping Side Effects and Withdrawal Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are once-weekly GLP-1/GIP receptor agonist injections licensed for weight management in UK adults, yet they work slightly differently. Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy activates GLP-1 only. This difference affects side effect profiles during treatment, but the withdrawal experience is broadly similar: both medications clear the system within 2–4 weeks, and both allow side effects to resolve relatively quickly.
In clinical trials (SURMOUNT for Mounjaro and STEP for Wegovy), participants who discontinued either medication experienced comparable weight regain patterns. Neither medication has a specific "rebound" syndrome with serious withdrawal effects. The primary concern after stopping is lifestyle adherence—if you return to your pre-treatment eating and exercise patterns, weight is likely to return. A prescriber can discuss with you which medication might be more suitable based on your individual health profile, eligibility, and clinical assessment. Our GLP-1 weight loss calculator can help you understand projected outcomes on either medication before discussing with your GP or prescriber.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Do Mounjaro side effects stop immediately after your last injection?
Most Mounjaro side effects—particularly nausea, diarrhoea, and constipation—resolve within 1–2 weeks of stopping. However, appetite suppression and some metabolic changes may persist slightly longer. Tirzepatide is a once-weekly injection, so each dose clears over several days. Always discuss stopping Mounjaro with your prescriber; do not stop abruptly without guidance.
Will I regain weight after stopping Mounjaro?
Weight regain is likely if you return to your previous eating and exercise habits. SURMOUNT trial data showed that without continued calorie deficit and physical activity, participants gradually regained weight after stopping. The rate varies individually. Maintaining the dietary and lifestyle changes you developed during treatment is key to sustaining weight loss.
Is stopping Mounjaro dangerous or does it cause withdrawal?
Stopping Mounjaro does not cause serious withdrawal symptoms or dangerous rebound effects. The medication gradually leaves your system over 2–4 weeks. However, you should not stop suddenly without consulting your prescriber—they may recommend a gradual approach or transition to alternative strategies to maintain progress.
How does stopping Wegovy compare to stopping Mounjaro?
Both medications are once-weekly injections and have similar withdrawal profiles. Side effects resolve within 1–2 weeks for both. Weight regain patterns are comparable and depend primarily on lifestyle adherence. The choice between them is based on individual suitability, clinical assessment, and prescriber recommendation—both are prescription-only in the UK.
What should I do before stopping Mounjaro?
Discuss stopping with your GP or prescriber before your final injection. They can advise whether a gradual approach or transition plan might help maintain your progress. Plan to continue the dietary and exercise habits you developed during treatment—these are crucial to preventing rapid weight regain. Consider tracking your weight using our free progress tracker to monitor changes after stopping.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.